Image Sensor Kick-Back Noise Blocking Circuit
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Solution Overview
Problem
CMOS image sensors experience switching noise during the conversion of analog signals to digital signals through oversampling, which is then transferred back to the pixel units, causing kick-back noise.
Innovation Solution
Incorporating a kick-back noise blocking circuit, such as a resistor or MOSFET, between the column line and the signal process circuit, along with a signal process circuit that includes a correlated double sampling circuit and an analog to digital converter, like a sigma-delta modulator and digital filter, to reduce switching noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a switching operation is performed to convert analog signal to digital signal through oversampling, then signal conversion is achieved, but kick-back noise is generated and transferred to pixel units
Solution Approach 1:
A kick-back noise blocking circuit is introduced as an intermediary component between the pixel unit and the signal process circuit. This blocking circuit selectively prevents kick-back noise from the switching operation from being transferred back to the pixel unit, while allowing the desired analog signal to pass through for conversion to digital signal.
Solution Approach 2:
The signal processing system is segmented into distinct functional blocks: pixel unit, kick-back noise blocking circuit, and signal process circuit. This segmentation allows the blocking circuit to independently handle noise suppression without interfering with the overall signal conversion process.
2Object-affected harmful factors
If a kick-back noise blocking circuit is added to reduce switching noise, then noise interference is reduced, but device complexity increases
Solution Approach 1:
The kick-back noise blocking circuit serves as a dedicated intermediary component that specifically addresses noise interference. By placing this blocking circuit between the pixel unit and signal process circuit, noise suppression is achieved through a focused, specialized component rather than requiring complex modifications throughout the entire system.
Solution Approach 2:
The noise blocking function is extracted as a separate, independent circuit block from the main signal processing path. This extraction allows the blocking circuit to handle noise suppression independently, maintaining simplicity in the core signal conversion operations while adding only the necessary noise reduction capability.
Data Source
AI summary
An image sensor comprises a plurality of pixel units connected to a column line, a signal process circuit configured to process a signal output from the column line according to a switching operation, and a kick-back noise blocking circuit configured to reduce kick-back noise caused by the switching operation. Each of the pixel units includes a photoelectric conversion element. The kick-back noise blocking circuit is connected between the column line and the signal process circuit.